The knee joint is a compromise between mobility and stability. It is one of the most mobile joints in the body, at the expense of stability. Almost all injuries to the knee will restrict mobility. A frequent injury is associated with the patella tendon. The quadricep muscles connect to the quad tendon which attaches to the kneecap from above. The kneecap is attached to the tibia below by the patella tendon. When the knee bends the patella tendon stretches. When the bending is traumatic, the patella tendon tends to lift off of the tibia, sometimes taking some of the bone with it. This is particularly true of young athletes where the tendon has not yet totally osciffied. Another injury involves subluxation which is a misalignment of the joint occurring when the patella or kneecap moves laterally. Subluxation can also result in patella chondromalacia, having to do with the interface between the inner surface of the patella and the confronting ligaments and tendons.